Hybrid disk-cone extrusion die module having a spillover surface surrounding a planar seal surface

ABSTRACT

The present invention discloses an extrusion die module having a flat compression seal surrounded by a conical or otherwise angled spillover surface. The die module promotes a flat surface to flat surface compression seal outside of the flow distribution channels and promotes better streamlined flow and material combination than a traditional flat disk die module. The die module promotes a reduced overall diameter and wetted diameter in comparison to standard flat disk dies. In addition, the present invention relates to an extrusion die module having a spillover surface surrounding a planar sealing surface. Further, the present invention relates to a method for utilizing an extrusion die module with a conical or otherwise angled spillover surface to minimize the die surface area wetted by an intermediate layer in a multi-layer coextrusion process.

FIELD OF THE INVENTION

[0001] The present invention relates to an extrusion die module.Specifically, the present invention relates to an extrusion die modulehaving a flat compression seal and a conical or otherwise angledspillover surface. More specifically, the present invention relates toan extrusion die module having a spillover surface surrounding a planarseal surface. Further, the present invention relates to a method forutilizing an extrusion die module with a conical or otherwise angledspillover surface to minimize the die surface area wetted by anintermediate layer in an extrusion process involving at least threelayers.

BACKGROUND OF THE INVENTION

[0002] An extrusion die for extruding melt material for the creation offlexible films has typically included at least one module having one ora plurality of flow channels to distribute melt over a spilloversurface. The melt material may generally flow from the flow channelsonto the spillover surface to be extruded therefrom to form a flexiblefilm. In a typical flexible film “bubble” extruder, the module allowsmolten material to flow over a spillover surface to a gap between a diemodule and a central mandrel, whereupon a tube of plastic material maybe extruded through an annular portion of the extrusion die. The conceptalso applies to extrusion blow molding parisons, wire coating, pipeextrusion, tube extrusion, etc. Moreover, a plurality of modules may bestacked in series to extrude a plurality of layers into a tubularstructure. Each successive module may add a layer to the film structurewhen the molten material solidifies.

[0003] Extrusion die modules are typically nested cylinders, flat disk,or conical die modules. A flat disk module may allow a molten materialto flow through flow channels directly onto a flat spillover surfacelocated adjacent to the central mandrel. Each type of module typicallyconsists of a pair of matching portions, or matching halves, that may bedisposed one atop of another to form internal flow channels andspillover surfaces within the module. The matching halves may be boltedtogether to form a single extrusion die module, whereby the moltenmaterial may enter via the flow channels and may be extruded annularlyafter flowing over the spillover surface.

[0004] In melt extrusion, it is often desirable to streamline the flowof material from the flow surface of the module to the flow surface ofthe annular portion of the extrusion die. For example, the material flowmay be streamlined by changing the flow direction angle of the materialthrough the module and over the spillover surface by as small an angleas possible at any given point in the material flow. Flat disk extrusiondies are typically unable to generate a large degree of streamlinedmaterial flow because the plastic material generally flows through theflow channels of the module and over the spillover surface until itmeets the annular portion of the extrusion die. At the annular portionof the extrusion die, the plastic material flow direction changesapproximately 90 degrees to flow along the central mandrel that islocated perpendicular to the spillover surface of the die module.Conical extrusion die modules are typically better adapted for promotingstreamline material flow. The conical portion allows the flow directionangle to change less than 90 degrees as the material flows over thespillover surface and into the gap between the die module and themandrel.

[0005] Moreover, conical extrusion die modules are capable of having asmaller wetted diameter and a smaller overall diameter than similar flatdisk extrusion die modules. For example, the flow path of a conicalextrusion die module with a flow path entirely at 45 degrees to themodule axis needs only to be 71% (sine(45°)) of the radial length of aflat disk extrusion die module with the same area of spillover surface.Reducing both the wetted diameter and the overall die diameter has anumber of benefits. For example, less wetted diameter means lesshydraulic force is exerted by the melt material. Also, less overallmodule diameter means less module weight to support, move, and otherwisehandle. Similarly, less overall module diameter means less thermal massto heat and cool, thereby allowing for faster startups and changeoversand better thermal control. Each of the above effects may varyproportionally to the diameter of the die module squared (d²) thusenabling a small reduction in diameter to have a significant positiveeffect.

[0006] Leakage of molten material from the modules may cause manyproblems. For example, the plastic may leak out of the module to theambient environment, thereby wasting material and creating potentialhousekeeping and safety issues. Additionally, the plastic material maydegrade into carbon, gels, gas, and/or material of altered physical,chemical, and/or optical properties. Backflow of the degraded materialmay contaminate the extruded product. Further, plastic materials, suchas PVdC and PVC, may form corrosive byproducts, if allowed to leak anddegrade, and may lead to corrosion of the extrusion die. A damagedextrusion die is even more susceptible to leakage, leading to moredegradation, thereby leading to further corrosion. Moreover, plasticflow outside of the flow channel may act as a hydraulic fluid underpressure to exert forces against adjacent extrusion die modules or otherequipment. Consequently, the adjacent die modules may separate, causingfurther leakage and larger separating forces to be generated. Commonly,seal means are used to prevent plastic flow from leaking or otherwiseleaving the flow channel areas of the modules.

[0007] A number of seal means for extrusion die modules are presentlyused. For example, flat surface to flat surface compression seals may beutilized for flat disk dies. Moreover, matched taper seals may beutilized for conical dies. Flat surface to flat surface compressionseals are generally more effective than matched taper seals because thematched channels that are cut into matching conical die module halvesmay move out of alignment as the seals undergo surface wear. Surfacewear is particularly damaging for conical dies having the flow channelsdisposed on the spillover surface(s). Because the flow channels aredisposed on the angled portion of the spillover surface(s) of theconical die, surface wear causes the flow channels of the matchingmodule portions to fall out of alignment. As the conical die channelsmove out of alignment, the degradation areas may increase and theproblems discussed above may intensify. Conversely, as flat surfacecompression seal surfaces undergo surface wear, the matched channelsthat may be cut into the adjacent dies generally maintain theiralignment, because the matching module portions are horizontal and thedislocation effect is minimized.

[0008] In multi-layer plastic extrusion, it is often desirable tocombine certain material layers as early in the coextrusion system aspossible. For example, it is desirable to encapsulate degradation-pronelayers with more stable layers as soon as possible. Therefore, the morestable layers protect the degradation-prone layers from the heat of theextrusion system and decrease the time that the degradation-pronematerial is exposed to the heated surfaces of the extrusion system. In astandard flat disk die, the amount of time that a degradation-pronematerial may be exposed to heat of the annular portion of the die isrelated to the thickness of the extrusion die module itself.

[0009] When flat disk die modules and conical die modules are stacked inseries, the distances that the degradation-prone materials are exposedto the surfaces of the extrusion die module is related to the type ofdie module and order of placement of the die modules in the series.Material layers enter the annular portion of the extrusion die from theextrusion die modules separated by a distance approximately equal to thethickness of one die module, in the case of a first flat disk die modulepositioned downstream of a second flat disk die module. Similarly,material layers enter the annular portion of the extrusion die from theextrusion die modules separated by a distance approximately equal to thethickness of one die module in the case of a first conical die modulepositioned downstream of a second conical die module. Further, materiallayers enter the annular portion of the extrusion die from the extrusiondie modules separated by a distance approximately equal to one half thethickness of a flat disk die module in the case of a flat disk diemodule positioned downstream of a conical disk die module. Moreover,material layers typically enter the annular portion of the extrusion diefrom the extrusion die modules separated by a distance approximatelyequal to the thickness of a conical die module plus one half thethickness of a flat disk die module in the case of a conical disk diemodule positioned downstream of a flat disk die module. Therefore,stacking known flat disk and conical dies in series may cause adegradation-prone material to be exposed to the hot and potentiallydamaging surface of the die modules and/or the mandrel for at least onehalf of a die module. In many instances, it is beneficial to encapsulatea degradation prone material layer with a shorter distance between theentry of the multiple layers into the annular portion of the extrusiondie.

[0010] Accordingly, it is desirable to provide an extrusion die modulewith the flat surface compression sealing benefits of a flat diskextrusion die and the streamlined flow and reduced diameter benefits ofa conical extrusion die. Additionally, it would be beneficial to providea method of combining multiple material layers within a shorter distancealong the annular portion of the extrusion die to allowdegradation-prone materials to be encapsulated by more stable layers andto minimize the distance that a degradation-prone layer is exposed todirect contact with the walls of the extrusion die.

SUMMARY OF THE INVENTION

[0011] The present invention provides an extrusion die module.Specifically, the present invention relates to an extrusion die modulehaving a flat compression seal and a conical or otherwise angledspillover surface. Further, the present invention relates to a systemand a method for utilizing an extrusion die module with a conical orotherwise angled spillover surface to encapsulate an intermediate layerin an extrusion process involving at least three layers.

[0012] It is one of the principal objectives of the present invention toprovide an extrusion die module with a horizontal flat surface tohorizontal flat surface compression seal outside of the distributionchannels of the extrusion die module. It is another objective of thepresent invention to provide an extrusion die with a conical, arched, orvertically cylindrical spillover surface. In addition, it is anotherobjective of the present invention to provide an extrusion die modulehaving a spillover surface surrounding a planar seal surface.

[0013] It is yet another objective of the present invention to providean extrusion die module capable of being used to streamline the flow ofmaterial being extruded through the die module and through the annularportion of the extrusion die. It is still another objective of thepresent invention to provide an extrusion die module with a reducedoverall diameter.

[0014] It is moreover an objective of the present invention to providean extrusion die module with a reduced wetted diameter. It is a furtherobjective of the present invention to provide an extrusion die modulecapable of being used to combine layers of material flowing throughseparate dies modules with a minimum distance between the two entrypoints of the two layers into the annular portion of the extrusion die.

[0015] These and other objectives of the present invention will becomeapparent upon examining the drawings and figures together with theaccompanying written description thereof.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is an exploded perspective view of an extrusion die moduleof the present invention.

[0017]FIG. 2 is a top view of an upstream portion of an extrusion diemodule of the present invention.

[0018]FIG. 3 is a top view of a downstream portion of an extrusion diemodule of the present invention.

[0019]FIG. 4 is an exploded perspective view of another extrusion diemodule of the present invention.

[0020]FIG. 5 is a perspective view of stacked extrusion die modules,including two extrusion die modules of the present invention.

[0021]FIG. 6 is a cross-sectional view of an embodiment of stackedextrusion die modules, including two extrusion die modules of thepresent invention.

[0022]FIG. 7 is a cross-sectional view of another embodiment of stackedextrusion die modules, including two extrusion die modules of thepresent invention.

[0023]FIG. 8 is a cross-sectional view of another embodiment of thepresent invention, including a stacked extrusion die assembly having apair of extrusion dies wherein one extrusion die is disposed within theother extrusion die.

DETAILED DESCRIPTION OF THE DRAWINGS

[0024] The present invention relates to a die module that may be used toform extruded plastic products, such as, for example, flexible filmsfrom melt material. More specifically, the present invention may allow amelt material to be extruded through flow channels onto a conical orotherwise angled spillover surface. The flow channels may flow from aflat disk portion of the extrusion die module to the spillover surfaceto present a flat, horizontal sealing surface for the mating portions ofthe extrusion die. In addition, the spillover surface may be disposedoutside of the planar sealing surface. Moreover, the present inventionrelates to a plurality of extrusion die modules disposed in series toallow encapsulation of degradation-prone polymeric materials within theextrusion die.

[0025] Now referring to the Figures, wherein like numerical referencesrefer to like parts, FIG. 1 illustrates an embodiment of an extrusiondie module 10 of the present invention. As shown in FIG. 1, theextrusion die module 10 may include an upstream mating portion 12 and adownstream mating portion 14, collectively referred to herein as themating portions 12,14. The mating portions 12,14 may be coupled togetherto form the extrusion die module 10 and may be coupled together in anymanner apparent to one skilled in the art. For example, bolt holes 15a-15 h may be provided for bolting the mating portions 12,14 to eachother and to other extrusion die modules. The extrusion die module 10may be used in a cylindrical stacked extrusion die 39 (as shown in FIGS.5 and 6) for extruding plastic film or any other similar material. Ofcourse, the bolt holes may be disposed within the mating portions 12,14in any manner apparent to one having ordinary skill in the art andshould not be limited as herein described. Moreover, additional matchingbolt holes may be disposed within the mating portions 12,14 toeffectively seal mating portion 12 to mating portion 14.

[0026] The upstream mating portion 12 may include an inflow surface (notshown) and an outflow surface 16. The outflow surface 16 may include anupstream seal surface 18 and an upstream spillover surface 20. Thedownstream mating portion 14 may include a downstream flow surface 22having a downstream seal surface 24 and a downstream spillover surface26. Alternatively, the inflow surface may be located on the downstreammating portion 14. The upstream seal surface 18 and the downstream sealsurface 24 are collectively referred to herein as the seal surfaces18,24. The upstream spillover surface 20 and the downstream spilloversurface 26 are collectively referred to herein as the spillover surfaces20,26. Each of the spillover surfaces 20,26 may be conical, arced, or inthe extreme, cylindrical. Additionally, each of the spillover surfaces20,26 may be configured to include any combination of one or more anglesand radii.

[0027] For example, the upstream spillover surface 20 may transitionfrom the upstream seal surface 18 at an angle between zero and ninetydegrees, inclusively, or at an arc. In a preferred embodiment, theupstream spillover surface 20 may transition from the upstream sealsurface 18 at an angle of forty-five degrees.

[0028] In one embodiment, the spillover surfaces 20,26 may be designedto create a slit from a flow channel created between the spilloversurfaces 20,26 that is approximately {fraction (70/1000)} of an inchwide at an exit location 38 a,38 b of the mating portions 12, 14.Alternatively, the spillover surfaces 20,26 may be designed to createany sized and shaped flow channel that would be apparent to one skilledin the art. For example, it may be beneficial to create a flow channelwhose thickness varies along the radial length of the flow channel.Further, it may be beneficial to include a flow channel including one ormore radii to achieve desired flow characteristics. Non-linear flowchannel geometry may provide more uniform distribution of the meltmaterial as polymers generally exhibit non-linear flow characteristics.

[0029] When the mating portions 12,14 are coupled together, the sealsurfaces 18,24 may form a flat surface to flat surface compression sealsurrounding the spillover surfaces 20,26 as is further described below.Additionally, when the mating portions 12,14 are coupled together, aflow channel (as shown in FIG. 6) may be formed between the spilloversurfaces 20,26 as further described below.

[0030] Referring now to FIG. 2, one or more distribution passages 28a-28 d may be located in the upstream mating portion 12 for providing aflow path for plastic material to flow from the inflow surface (notshown) to the outflow surface 16 of the upstream mating portion 12. Thedistribution passages 28 a-28 d may be apertures that may allow meltmaterial to pass from the inflow surface to the outflow surface 16. Forexample, the distribution passages 28 a-28 d may be generally ovalshaped apertures as shown in FIG. 2. However, any other shaped aperturesmay be utilized without detracting from the present invention. In theembodiment of the present invention shown in FIG. 2, the distributionpassages 28 a-28 d may be located in the face of the flat upstream sealsurface 18. Consequently, in the embodiment shown in FIG. 2, the outerperimeters of the distribution passages 28 a-28 d may partially definethe inner perimeter of the seal surface 18 as further described below.Alternatively, the distribution passages 28 a-28 d may be configured inany manner apparent to one skilled in the art. For example, both theinflow surface and the distribution passages may be located in thedownstream mating portion 14.

[0031] Melt material may flow along the inflow surface (not shown) ofthe upstream mating portion 12, through the distribution passages 28a-28 d, and to the outflow surface 16 as would be apparent to oneskilled in the art. For example, there may be a inflow channel (notshown) located along the inflow surface of the upstream portion 12 fortransferring the melt material flow from an extruder to the distributionpassages 28 a-28 d. The inflow channel may be designed to provide a flowpath configuration wherein the flow of plastic material travels an equallinear distance along the inflow channel to arrive at each of thedistribution passages 28 a-28 d approximately simultaneously. The inflowchannel may be formed from a pair of matched half-channels cut intoadjacent surfaces of adjacent die mating portions, including theupstream mating portion 12. Alternatively, the inflow channel may beformed within the downstream mating portion 14.

[0032] In various embodiments of the present invention, the inflowchannel may be located on the outflow surface 16 of the upstream matingportion 12, on the downstream flow surface 22, or may be formed frommatching half-channels cut into the mating portion 12, 14 to eliminatethe need for the distribution passages 28 a-28 d. However, in apreferred embodiment, the inflow channel is located on the inflowsurface of the upstream mating portion 12, or on the inflow surface ofthe downstream mating portion 14, to help reduce the overall diameter ofthe extrusion die module 10. Of course, the melt material may betransferred to the distribution passages 28 a-28 d from the extruder inany manner apparent to one having ordinary skill in the art.

[0033] One or more upstream distribution channels 30 a-30 d may belocated on the outflow surface 16 of the upstream mating portion 12.Melt material may flow from the distribution passages 28 a-28 d to theupstream distribution channels 30 a-30 d. The number of upstreamdistribution channels 30 a-30 d may correspond to the number ofdistribution passages 28 a-28 d. Further, the upstream distributionchannels 30 a-30 d may be configured as matching half-channels formating with the downstream distribution channels 34 a-34 d when theupstream mating portion 12 is mated with the downstream mating portion14. In the embodiment illustrated in FIG. 2, there may be four spiralupstream distribution channels 30 a-30 d located symmetrically aroundthe axis of the upstream mating portion 12. Spiral upstream distributionchannels 30 a-30 d may be employed to avoid developing a radial weldline in the extruded plastic film as may be developed by a cross-headdie. Additionally, utilizing a plurality of symmetrical spiral channelsmay improve the flow characteristics of plastic material as it flowsover the outflow surface 16 of the upstream mating portion 12.Alternatively, there may be any number of upstream distribution channels30 a-30 d arranged in any configuration as would be apparent to oneskilled in the art.

[0034] In the embodiment shown in FIG. 2, the portions of the upstreamdistribution channels 30 a-30 d adjacent to the distribution passages 28a-28 d are located in the upstream seal surface 18. As the upstreamdistribution channels 30 a-30 d spiral inwardly towards the innerdiameter of the upstream mating portion 12, the upstream distributionchannels 30 a-30 d transition out of the flat plane of the upstream sealsurface 18 and onto the plane of the upstream spillover surface 20.Consequently, the outer perimeters of the upstream distribution channels30 a-30 d may partially define the inner perimeter of the upstream sealsurface 18 as further described below.

[0035] The upstream distribution channels 30 a-30 d may vary in depthand length as may be apparent to one having ordinary skill in the art.For example, the upstream distribution channels 30 a-30 d may be aparticular depth when the melt material flows from the upstreamdistribution passages 28 a-28 d but may decrease in depth as the meltmaterial flows along the upstream distribution channels 30 a-30 d untilthe depth of the upstream distribution channels 30 a-30 d is zero,relative to the surface that the distribution channels are disposed in,at points 31 a-31 d. Moreover, the length and distance between theupstream distribution channels 30 a-30 d may vary. This may allow theupstream distribution channels 30 a-30 d to evenly distribute the meltmaterial on the spillover surface 20, depending on the properties of themelt material, such as, for example, the viscosity of the material.

[0036] The geometry of the upstream distribution channels 30 a-30 d inthe upstream spillover surface 20 is typically designed through the useof proprietary design software. The software typically analyzes thematerial to be extruded as well as the temperature, pressure, and rateof extrusion to determine the proper geometry for the upstreamdistribution channels 30 a-30 d the upstream spillover surface 20. Forexample, with all other factors held constant, a material with a higherviscosity may require wider or deeper upstream distribution channels 30a-30 d than a material with a lower viscosity.

[0037] There may be one or more upstream seal surface boundaries 32 a-32d located along the outflow surface 16 of the upstream mating portion 12as shown in FIG. 2. The number of upstream seal surface boundaries 32a-32 d may correspond to the number of upstream distribution passages 28a-28 d and the number of upstream distribution channels 30 a-30 d. Theupstream seal surface boundaries 32 a-32 d may separate the upstreamseal surface 18 from the upstream spillover surface 20. Consequently, asshown in FIG. 2, the inner perimeter of the upstream seal surface 18 maybe defined by the outer perimeters of the distribution passages 28 a-28d, the outer perimeter of the upstream distribution channels 30 a-30 d,and the upstream seal surface boundaries 32 a-32 d.

[0038] For example, as illustrated in FIG. 2, the outer perimeter of theseal surface 18 may be located along the outer perimeter of the outflowsurface 16. The inner perimeter of the seal surface 18 may trace a paththat follows the length of the upstream seal surface boundaries 32 a-32d to the outer perimeters of the distribution passages 28 a-28 d, alongthe outer perimeters of the distribution passages 28 a-28 d (in acounter-clockwise direction) towards the outer perimeters of theupstream distribution channels 30 a-30 d, and along the outer perimetersof the upstream distribution channels 30 a-30 d to the adjacent upstreamseal surface boundaries 32 a-32 d. Thus, the distribution passages 28a-28 d and the upstream distribution channels 30 a-30 d may be locatedentirely within the inner perimeter of the upstream seal surface 18.Consequently, the upstream seal surface 18 may be the portion of theoutflow surface 16 of the upstream mating portion 12 located between theouter perimeter of the outflow surface 16 and the outer perimeters ofthe distribution passages 28 a-28 d, the outer perimeters of theupstream distribution channels 30 a-30 d, and the upstream seal surfaceboundaries 32 a-32 d.

[0039] The outer perimeter of the upstream seal surface 18 may bedefined by the outer perimeter of the outflow surface 16 of the upstreammating portion 12. Alternatively, the outer perimeter of the upstreamseal surface 18 may be defined in any manner apparent to one skilled inthe art. For example, the outer perimeter of the upstream seal surface18 may end where the plurality of bolt holes 15 a-h may be disposed.

[0040] Turning now to FIG. 3, a downstream mating portion 22 may beconfigured as shown. One or more downstream distribution channels 34a-34 d may be located on the downstream flow surface 22 of thedownstream mating portion 14. The downstream flow surface 22 may behorizontal and planar. The number of downstream distribution channels 34a-34 d may correspond to the number of upstream distribution channels 30a-30 d. In the preferred embodiment illustrated in FIG. 3, there may befour spiral downstream distribution channels 34 a-34 d locatedsymmetrically around the axis of the downstream mating portion 14.Moreover, the downstream distribution channels 34 a-34 d may beconfigured as matching half-channels for mating with the upstreamdistribution channels 30 a-30 d when the upstream mating portion 12 ismated with the downstream mating portion 14. Alternatively, there may beany number of downstream distribution channels 34 a-34 d arranged in anyconfiguration as would be apparent to one skilled in the art. Asdescribed above with reference to the upstream distribution channels 30a-30 d, the geometry of the downstream distribution channels 34 a-34 dis typically designed through the use of proprietary design software.

[0041] In the embodiment shown in FIG. 3, the portions of the downstreamdistribution channels 34 a-34 d located furthest from the axis of thedownstream mating portion 14 may be located in the horizontal, planardownstream seal surface 24. Similar to the upstream distributionchannels 30 a-30 d described above, as the downstream distributionchannels 34 a-34 d spiral inwardly towards the inner diameter of thedownstream mating portion 14, the downstream distribution channels 34a-34 d may transition out of the flat plane of the downstream sealsurface 24 and onto the plane of the downstream spillover surface 26.Consequently, the outer perimeters of the downstream distributionchannels 34 a-34 d may partially define the inner perimeter of thedownstream seal surface 24 as further described below.

[0042] There may be one or more downstream seal surface boundaries 36a-36 d located along the downstream flow surface 22 of the downstreammating portion 14, as shown in FIG. 3. The number of downstream sealsurface boundaries 36 a-36 d may correspond to the number of upstreamseal surface boundaries 32 a-32 d. The downstream seal surfaceboundaries 36 a-36 d may separate the downstream seal surface 24 fromthe downstream spillover surface 26. Consequently, as shown in FIG. 3,the inner perimeter of the downstream seal surface 22 may be defined bythe outer perimeters of the downstream distribution channels 34 a-34 dand the downstream seal surface boundaries 36 a-36 d.

[0043] For example, as illustrated in FIG. 3, the outer perimeter of thedownstream seal surface may be defined by the outer perimeter of thedownstream flow surface 22 of the downstream mating portion 14. Theinner perimeter of the downstream seal surface 24 may trace a path thatfollows the length of the downstream seal surface boundaries 36 a-36 dand along the outer perimeters of the downstream distribution channels34 a-34 d to the adjacent downstream seal surface boundaries 36 a-36 d.Thus, the downstream distribution channels 34 a-34 d may be locatedentirely within the inner perimeter of the downstream seal surface 24.Consequently, the downstream seal surface 24 may be the portion of thedownstream flow surface 22 of the downstream mating portion 14 locatedbetween the outer perimeter of the downstream flow surface 22 and theouter perimeters of the downstream distribution channels 34 a-34 d andthe downstream seal surface boundaries 36 a-36 d.

[0044] The outer perimeter of the downstream seal surface 24 may bedefined by the outer perimeter of the downstream flow surface 22 of thedownstream mating portion 14. Alternatively, the outer perimeter of thedownstream seal surface may be defined in any manner apparent to oneskilled in the art.

[0045] As molten plastic flows out of the distribution passages 28 a-28d, the molten plastic may flow along the flow channels that may beformed by the mating portions of the distributions channels 30 a-30 d,as shown in FIG. 2, and the distribution channels 34 a-34 d, as shown inFIG. 3. As the melt material flows along these flow channels, the meltmaterial spills over onto the upstream spillover surface 20 (of theupstream mating portion 14) and the downstream spillover surface 26 (ofthe downstream mating portion 22) through the flow channel formedtherebetween. As the melt material spills over onto the spilloversurfaces 20,26, the melt material may be evenly distributed over thespillover surfaces 20,26 to form a continuous tube of melt material thatmay exit the extrusion module 10 at the exit locations 38 a,38 b of themating portions 12,14, respectively.

[0046]FIG. 4 illustrates another embodiment of an extrusion die module200 of the present invention. As shown in FIG. 4, the extrusion diemodule 200 may include an upstream mating portion 202 and a downstreammating portion 204, collectively referred to herein as the matingportions 202,204. Additionally, the upstream mating portion 202 mayinclude an upstream seal surface 206 and the downstream mating portion204 may include a downstream seal surface 208, collectively referred toherein as the seal surfaces 206,208. Further, the upstream matingportion 202 may include an upstream spillover surface 210 and thedownstream mating portion 204 may include a downstream spillover surface212, collectively referred to herein as the spillover surfaces 210,212.Moreover, the upstream mating portion 202 may include an inflow passage213, one or more upstream inflow channels 214 a-214 d, and one or moreupstream distribution channels 216 a-216 h. Similarly, the downstreammating portion 204 may include one or more downstream inflow channels215 a-215 d as well as one or more downstream distribution channels 218a-218 h. The upstream inflow channels 214 a-214 d and the downstreaminflow channels 215 a-215 d are collectively referred to herein as theinflow channels 214 a-214 d,215 a-215 d. The upstream distributionchannels 216 a-216 h and the downstream distribution channels 218 a-218h are collectively referred to herein as the distribution channels 216a-216 h,218 a-218 h.

[0047] As shown in FIG. 4, the spillover surfaces 210,212 and thedistribution channels 216 a-216 h,218 a-218 h may be located entirelyoutside the outer perimeter of the seal surfaces 206,208. The outerperimeter of the upstream seal surface 206 may be partially defined byseal surface boundaries 220 a-220 h. Moreover, the outer perimeter ofthe downstream seal surface 208 may be partially defined by seal surfaceboundaries 220 i-220 p. The spillover surfaces 210,212, the inflowchannels 214 a-214 d,215 a-215 d and the distribution channels 216 a-216h,218 a-218 h may be configured to provide flat-surface to flat-surfacecompression seal surfaces 206,208 surrounded by conical spilloversurfaces 210,212. The embodiment of the extrusion die module 200illustrated in FIG. 4 may also include one or more bolt holes (notshown) as described above with respect to FIG. 2.

[0048] The inflow passage 213 may be centrally located in the upstreammating portion 202 as shown in FIG. 4. Alternatively, the inflow passage213 may be offset from the central axis of the upstream mating portion202 in any position apparent to one having ordinary skill in the art.Melt material may flow from an extruder (not shown) through the inflowpassage 213 to the upstream mating portion 202. The extruder may beconnected to the inflow passage 213 by an extrusion tube (not shown)passing through extrusion die modules disposed beneath the upstreammating portion 202. Alternatively, an inflow passage may be disposedwithin the downstream mating portion 204 and an extrusion tube may beconnected to the inflow passage in the downstream mating portion 204 andmay pass through the extrusion die modules disposed above the upstreammating portion 204. In a multi-layer extrusion die 139 (FIG. 7)including one or more of the extrusion die modules 200 of the presentinvention, it may be beneficial to utilize offset inflow passages toallow a plurality of extruders to be connected to a plurality ofupstream mating portions 202.

[0049]FIG. 5 illustrates an embodiment of a cylindrical stackedextrusion die 39 of the present invention. The cylindrical stackedextrusion die 39 may include one or a plurality of the extrusion diemodule 10 as described above with reference to FIGS. 1-3. Referencenumerals 110 a, 110 b in FIG. 5 refer to extrusion die modules asdescribed, with reference to FIGS. 1-3, as the extrusion die module 10.In addition to the extrusion die modules 110 a, 110 b of the presentinvention, the cylindrical stacked extrusion die 39 may include one or aplurality of flat disk die modules 40 a-40 i. As an alternative to, orin addition to the flat disk die module portions 40 a-40 i, thecylindrical stacked extrusion die 39 may include one or a plurality ofthe conical extrusion die module 10 (not shown) or any other extrusiondie modules apparent to one skilled in the art.

[0050] The cylindrical stacked extrusion die 39 may also includeadditional module portions 41 a,41 b adjacent to the upstream matingportions 112 a,112 b, respectively, for forming inflow channels asdescribed above. Reference numerals 112 a,114 a and 112 b,114 b refer tomating portions, as described with reference to FIGS. 1-3, as matingportions 12,14. An end cap 43 may be utilized as the uppermost module inthe cylindrical stacked extrusion die 39. A central mandrel 42 may belocated along the vertical axis of the cylindrical stacked extrusion die39. An exit orifice 45 may be formed at the top of a central flowchannel 44 (shown in FIG. 6).

[0051]FIG. 6 illustrates a cross-sectional view of an embodiment of thecylindrical stacked extrusion die 39 shown in FIG. 5. The cylindricalstacked extrusion die 39 shown in FIG. 6 may include two extrusion diemodules 110 a,110 b having additional module portions 41 a, 41 brespectively, and three flat disk extrusion die modules 60 a-60 c,comprising extrusion die module portions 40 a-40 c, 40 d-40 f, and 40g-40 i, respectively. Alternatively, the cylindrical stacked extrusiondie 39 may include any number of extrusion die modules 110 a,110 b, and60 a-60 c as may be apparent to one skilled in the art. The centralmandrel 42 may be located along the vertical axis of the cylindricalstacked extrusion die 39 as described above. The cylindrical stackedextrusion die 39 may include a central flow channel 44 having an innerdiameter 46 which is defined by the outer diameter of the centralmandrel 42 and an outer diameter 48 which is defined by the surfaceformed by the inner diameter of the extrusion die modules 110 a,110 b,and 60 a-60 c and the inner surface of the end cap 43. Alternatively,the central flow channel 44 may be formed in any manner apparent to oneskilled in the art.

[0052] The stacked extrusion die modules 110 a,110 b, and 60 a-60 c mayform one or a plurality of outflow channels 50 a-50 e for passing meltmaterial from one or a plurality of plastic extruders (not shown) to thecentral flow channel 44. For example, the spillover surfaces 120 a,120b, and 126 a,126 b of the extrusion die modules 110 a, 110 bcorresponding to spillover surfaces 20, 26 of the extrusion die module10 shown in FIGS. 1-3, may form one or a plurality of the outflowchannels 50 c,50 d. Alternatively, there may be any number of outflowchannels 50 a-50 e that may be formed in any manner apparent to oneskilled in the art.

[0053] Melt material may flow from the outflow channels 50 a-50 e to thecentral flow channel 44 to form a multi-layered plastic extrudate. Amulti-layered plastic film, having a number of layers equal to thenumber of outflow channels 50 a-50 e, may be extruded from thecylindrical stacked extrusion die 39. For example, a five layeredplastic film may be extruded in the cylindrical stacked extrusion die39. Alternatively, a multi-layered film having any number of layersapparent to one skilled in the art may be extruded in the cylindricalstacked extrusion die 39 depending on the number of extrusion diemodules are present in the extrusion die.

[0054] A first layer of melt material may flow from the outflow channel50 a into the central flow channel 44. The first layer of melt materialmay flow along the both the inner diameter 46 and the outer diameter 48of the central flow channel 44 until the molten material reaches theoutflow channel 50 b. A second layer of melt material may flow from thesecond outflow channel 50 b into the central flow channel 44. As thesecond layer of melt material enters the central flow channel 44, thefirst layer of melt material may continue to flow along the innerdiameter 46 of the central flow channel 44, and the second layer of meltmaterial may flow along the outer diameter 48 of the central flowchannel 44 until the outflow channel 50 c.

[0055] A third layer of melt material may flow from the third outflowchannel 50 c into the central flow channel 44. As the third layer ofmelt material enters the central flow channel 44, the first layer ofmelt material may continue to flow along the inner diameter 46 of thecentral flow channel 44, the third layer of melt material may flow alongthe outer diameter 48 of the central flow channel 44 until the outflowchannel 50 d. When the third melt material enters the central flowchannel 44, the second layer of melt material may be encapsulatedbetween the first and third layers of melt material. However, at thispoint, the second layer of melt material will have traveled along thehot outer diameter of the central flow channel 44 between the outflowchannel 50 b and the outflow channel 50 c. The third outflow channel 50c may be formed by the extrusion die module 110 a. Further, the thirdoutflow channel 50 c may streamline the flow of the third layer of meltmaterial into the central flow channel 44.

[0056] A fourth layer of melt material may flow from the fourth outflowchannel 50 d into the central flow channel 44. As the fourth layer ofmelt material from the fourth outflow channel 50 d enters the centralflow channel 44, the third layer of melt material may be instantlyencapsulated between the second and fourth layers of melt materialwithout contacting the hot outer diameter 48. The fourth outflow channel50 d may also be formed by the extrusion die module of the presentinvention 110 b. Further, the fourth outflow channel 50 d may beconfigured such that the fourth layer of melt material flows into thecentral flow channel 44 against the flow of the first three layers ofmelt material. In such a configuration, the third layer of melt materialis encapsulated between the second and fourth layers of melt materialwith minimal exposure to the outer diameter 48 of the central flowchannel 44 because the fourth layer of melt material enters the centralflow channel 44 a minimal distance downstream of the point at which thethird layer of melt material enters the central flow channel 44.

[0057] A fifth layer of melt material may flow from the outflow channel50 e into the central flow channel 44. As the fifth layer of meltmaterial enters the central flow channel 44, the fifth layer of meltmaterial may flow along the outer diameter 48 of the central flowchannel 44, encapsulating the fourth layer of melt material between thethird and fifth molten plastic layers.

[0058] Further, any number of additional outflow channels 50 a-50 e maybe utilized in the cylindrical stacked extrusion die 39 such that eachsuccessive outflow channel 50 a-50 e may introduce a layer of meltmaterial to the central flow channel 44.

[0059] The extrusion die modules 110 a,110 b of the present inventionmay be utilized in the cylindrical stacked extrusion die 39 tostreamline the flow of melt material into the central flow channel 44 aswould be apparent to one skilled in the art. Additionally, the extrusiondie modules 110 a, 110 b of the present invention may be utilized in thecylindrical stacked extrusion die 39 to combine multiple melt materiallayers within a shorter distance along the central flow channel 44 toallow degradation-prone materials to be instantly encapsulated by morestable layers and to minimize the distance that a degradation-pronelayer is exposed to direct contact with the walls of the extrusion diemodules 110 a,110 b, and 60 a-60 c.

[0060] For example, in an embodiment of the cylindrical stackedextrusion die 39 of the present invention, a multi-layered plastic filmhaving five layers may be extruded. The five-layered film may include,for example, an outer abuse layer, a first tie layer, a barrier layer, asecond tie layer, and an inner sealant layer. For example, the outerabuse layer and the inner sealant layer may be any structural plasticmaterial apparent to one skilled in the art. Additionally, the barrierlayer may be methyl acrylate-polyvinylidene chloride copolymer (alsoknown as MA-PVdC or MA-Saran®) or another halogenated polymer.Similarly, the barrier layer may be ethylene vinyl alcohol copolymer(EVOH), a polyketone, a styrene acrylonitrile copolymer such as thepolymer manufactured by BP Amoco under the trademark Barex® Resins, apolyhydroxy ether or polyphenoxy ether such as the thermoplastic resinmanufactured by The Dow Chemical Company under the trademark BLOX®, orany other material apparent to one skilled in the art that may besensitive to high temperatures, high dwell time, and metal contact andmay be utilized as an internal layer of the film structure. Further, thefirst tie layer and the second tie layer may be any material used tobind the barrier material to the outer abuse layer and/or the innersealant layer. Moreover, the first tie layer and the second tie layermay be less degradation-prone than the barrier layer.

[0061] In the embodiment illustrated in FIG. 6, the inner sealant layermay enter the central flow channel 44 through the first outflow channel50 a and may flow along the both the inner diameter 46 and the outerdiameter of the central flow channel 44 until the second outflow channel50 b. The second tie layer may enter the central flow channel 44 throughthe second outflow channel 50 b and may flow along the outer diameter 48of the central flow channel 44 until the third outflow channel 50 c, andthe inner sealant layer may flow along only the inner diameter 46 of thecentral flow channel 44.

[0062] The degradation-prone barrier layer may enter the central flowchannel 44 through the third outflow channel 50 c. The inner sealantlayer may continue to flow along the inner diameter 46 of the centralflow channel 44 and the second tie layer may be encapsulated between theinner sealant layer and the barrier layer.

[0063] The first tie layer may enter the central flow channel 44 througha fourth outflow channel 50 d, instantly encapsulating the barrier layerbetween the first and second tie layers. The extrusion die module 110 bof the present invention having the fourth outflow channel 50 d may beconfigured such that the spillover surfaces 120 b,126 b direct the flowof the first tie layer against the flow of the material in the centralflow channel 44. Consequently, the first tie layer may enter the centralflow channel 44 a minimal distance along the central flow channel 44from the entry of the barrier layer to allow the degradation-pronebarrier layer to be encapsulated by the more stable first and second tielayers. This configuration may minimize the distance that thedegradation-prone layer is exposed to direct contact with the hot outerdiameter 48 of the central flow channel 44.

[0064] The outer abuse layer may enter the central flow channel 44through the fifth outflow channel 50 e and may flow along the outerdiameter 48 of the central flow channel 44, instantly encapsulating thefirst and second tie layers and the barrier layer between the outerabuse layer and the inner sealant layer. The five layer structure asherein described may then be extruded through the exit orifice 45whereupon the molten material may solidify into solid flexible films,tubes, molded articles, etc. upon the application of cooling means.

[0065]FIG. 7 illustrates a cross-sectional view of another embodiment ofa cylindrical stacked extrusion die 139 of the present invention. Thecylindrical stacked extrusion die 139 shown in FIG. 7 may include twoextrusion die modules 1200 a,1200 b of the present invention. Referencenumerals 1200 a,1200 b, comprising extrusion die mating portions 402a,404 a and 402 b,404 b respectively, refer to extrusion die modules asdescribed, with reference to FIG. 4, as extrusion die module 200 havingmating portions 202,204. In addition to the extrusion die modules 1200a,1200 b of the present invention, the cylindrical stacked extrusion die139 may include one or a plurality of flat disk die modules 160 a-160 cthat may comprise flat disk extrusion die module mating portions 140 a,140 b; 140 c,140 d; and 140 e, 140 f, respectively. Alternatively, thecylindrical stacked extrusion die 139 may include any number ofextrusion die modules 1200 a,1200 b, and 160 a-160 c apparent to oneskilled in the art. An outer housing 142 may surround the cylindricalstacked extrusion die 139 creating a flow channel 144 having an innerdiameter 146 which is defined by the surface formed by the outerdiameter of extrusion die modules 1200 a,1200 b, and 140 a-140 f and theouter surface of an end cap 143. The flow channel 144 may also have anouter diameter 148 that is defined by the inner diameter of the outerhousing 142. Alternatively, the flow channel 144 may be formed in anymanner apparent to one skilled in the art.

[0066] The stacked extrusion die modules 1200 a,1200 b, and 160 a-160 cmay form one or a plurality of outflow channels 150 a-150 e for passingmelt material from one or a plurality of plastic extruders (not shown)to the flow channel 144. For example, spillover surfaces 240 a,240 b,and 242 a,242 b of the extrusion die modules 1200 a,1200 b,corresponding to the spillover surfaces 210 and 212, respectively, ofthe extrusion die module mating portions 202,204, as described abovewith reference to FIG. 4, may form one or a plurality of the outflowchannels 150 c,150 d. Alternatively, there may be any number of outflowchannels 150 a-150 e that may be formed in any manner apparent to oneskilled in the art.

[0067] Melt material may flow from the outflow channels 150 a-150 e tothe flow channel 144 to extrude a multi-layered plastic extrudate. Amulti-layered plastic film, having a number of layers equal to thenumber of outflow channels 150 a-510 e, may be extruded in thecylindrical stacked extrusion die 139. For example, a five layeredplastic film may be extruded in the cylindrical stacked extrusion die139. Alternatively, a multi-layered film having any number of layersapparent to one skilled in the art may be extruded in the cylindricalstacked extrusion die 139.

[0068] A first layer of melt material may flow from a first outflowchannel 150 a into the flow channel 144. The first layer of meltmaterial may flow along the both the inner diameter 146 and the outerdiameter 148 of the flow channel 144 until the molten material reaches asecond outflow channel 150 b. A second layer of melt material may alsoflow from the second outflow channel 150 b into the flow channel 144. Asthe second layer of melt material enters the flow channel 144, the firstlayer of melt material may continue to flow along the outer diameter 148of the flow channel 144, and the second layer of melt material may flowalong the inner diameter 146 of the flow channel 144 until a thirdoutflow channel 150 c.

[0069] A third layer of melt material may also flow from the thirdoutflow channel 150 c into the flow channel 144. As the third layer ofmelt material enters the flow channel 144, the first layer of meltmaterial may continue to flow along the outer diameter 148 of the flowchannel 144, the third layer of melt material may flow along the innerdiameter 146 of the flow channel 144 until a fourth outflow channel 150d, and the second layer of melt material may be encapsulated between thefirst and third layers of melt material. The third outflow channel 150 cmay be formed by the extrusion die module of the present invention 1200a. Further, the third outflow channel 150 c may streamline the flow ofthe third layer of melt material into the flow channel 144.

[0070] A fourth layer of melt material may flow from the fourth outflowchannel 150 d into the flow channel 144. As the fourth layer of meltmaterial from the fourth outflow channel 150 d enters the flow channel144, the third layer of melt material may be instantly encapsulatedbetween the second and fourth layers of melt material. The fourthoutflow channel 150 d may be formed by the extrusion die module of thepresent invention 1200 a. Further, the fourth outflow channel 150 d maybe configured such that the fourth layer of melt material flows into theflow channel 144 against the flow of the first three layers of meltmaterial. In such a configuration, the third layer of melt material isencapsulated between the second and fourth layers of melt material withminimal exposure to the inner diameter 146 of the flow channel 144because the fourth layer of melt material enters the flow channel 144 aminimal distance downstream of the point at which the third layer ofmelt material enters the flow channel 144.

[0071] A fifth layer of melt material may flow from the fifth outflowchannel 150 e into the flow channel 144. As the fifth layer of meltmaterial enters the flow channel 144, the fifth layer of melt materialmay flow along the inner diameter 146 of the flow channel 144,encapsulating the fourth layer of melt material between the third andfifth molten plastic layers.

[0072] Further, any number of additional outflow channels may beutilized in the cylindrical stacked extrusion die 139 such that eachsuccessive outflow channel may introduce a layer of melt material to theflow channel 144.

[0073] The extrusion die modules 1200 a,1200 b of the present inventionmay be utilized in the cylindrical stacked extrusion die 139 tostreamline the flow of melt material into the flow channel 144 as wouldbe apparent to one skilled in the art. Additionally, the extrusion diemodules 1200 a,1200 b of the present invention may be utilized in thecylindrical stacked extrusion die 139 to combine multiple melt materiallayers within a shorter distance along the flow channel 144 to allowdegradation-prone materials to be encapsulated by more stable layers andto minimize the distance that a degradation-prone layer is exposed todirect contact with the walls of the extrusion die modules 1200 a,1200b, and 140 a-140 f

[0074]FIG. 8 illustrates another embodiment of the extrusion die of thepresent invention. In FIG. 8, a first set of stacked extrusion diemodules 300 and a second set of stacked extrusion die modules 302 may becombined to form an extrusion die assembly 304. The first set of stackedextrusion die modules 300 may comprise a series of extrusion die modulesas shown and described with reference to FIG. 7. The second set ofstacked extrusion die modules 302 may comprise a series of extrusion diemodules as shown and described with reference to FIG. 6. The first setof extrusion die modules 300 may be located along the central axis ofthe second set of extrusion die modules 302, in place of the centralmandrel shown in FIG. 6. Consequently, a flow channel 306 may be locatedbetween the outer diameter of the first set of extrusion die modules 300and the inner diameter of the second set of extrusion die modules 302.Therefore, a greater number of outflow channels per given extrusion dieheight may be provided in this embodiment of the extrusion die than ineither of the embodiments shown in FIGS. 6 or 7. The extrusion diemodules in the first set of stacked extrusion die modules 300 and thesecond set of stacked extrusion die modules 302 are not intended to belimited to the extrusion die modules disclosed herein. The extrusion dieassembly 304 may include any extrusion die modules that may beconfigured such that the first set of extrusion die modules may belocated within the second set of extrusion die modules.

[0075] It should be noted that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications may be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is, therefore, intendedthat such changes and modifications be covered by the appended claims.

We claim:
 1. An extrusion die module comprising: a first mating portioncomprising: a first planar seal surface having an outer perimeterdisposed in a plane; a first spillover surface, disposed entirelyoutside of said outer perimeter of said first planar seal surface anddisposed, at least in part, outside of said plane; and a firstdistribution channel disposed in said first spillover surface fordistributing melt material along said first spillover surface; and asecond mating portion comprising a second planar seal surface having aperimeter.
 2. The extrusion die module of claim 1 wherein said firstspillover surface is conical.
 3. The extrusion die module of claim 1further comprising a second spillover surface disposed adjacent to saidperimeter of said second planar seal surface.
 4. The extrusion diemodule of claim 1 wherein said first distribution channel furthercomprises a plurality of spiral distribution channels symmetricallyconfigured along said first spillover surface.
 5. The extrusion diemodule of claim 1 wherein said second mating portion further comprises asecond distribution channel disposed in said second seal surface fordistributing melt material along said second spillover surface.
 6. Amodular extrusion die assembly comprising: a plurality of extrusion diemodules disposed in series having an upstream end and a downstream end,wherein a first extrusion die module comprises: a first mating portioncomprising: a first planar seal surface having an outer perimeterdisposed in a plane; a first spillover surface, disposed entirelyoutside of said outer perimeter of said first planar seal surface anddisposed, at least in part, outside of said plane; and a firstdistribution channel disposed in said first spillover surface, fordistributing melt material along said first spillover surface; and asecond mating portion comprising a second planar seal surface having aperimeter.
 7. The modular extrusion die assembly of claim 6 wherein saidfirst mating portion of said first extrusion die module is disposedcloser to said upstream end of said modular extrusion die assembly thansaid second mating portion.
 8. The modular extrusion die assembly ofclaim 6 wherein a second extrusion die module comprises: a first matingportion comprising: a first planar seal surface having an outerperimeter disposed in a plane; a first spillover surface, disposedentirely outside of said outer perimeter of said first planar sealsurface and disposed, at least in part, outside of said plane; and afirst distribution channel disposed in said first seal surface, fordistributing melt material along said first spillover surface; and asecond mating portion comprising a second planar seal surface having aperimeter.
 9. The modular extrusion die assembly of claim 8 wherein saidsecond mating portion of said first extrusion die module is disposedadjacent to said second mating portion of said second extrusion diemodule.
 10. The modular extrusion die assembly of claim 8 wherein saidfirst spillover surface and said second spillover surface are conical.11. A method of extruding molten plastic resin through an extrusion dieassembly comprising the steps of: providing an extrusion die modulecomprising: a first mating portion comprising: a first planar sealsurface having an outer perimeter disposed in a plane; a first spilloversurface, disposed entirely outside of said outer perimeter of said firstplanar seal surface and disposed, at least in part, outside of saidplane; and a first distribution channel disposed in said first sealsurface, for distributing melt material along said first spilloversurface; and a second mating portion comprising a second planar sealsurface having a perimeter; and extruding melt material through saidextrusion die module to form an extrudate.
 12. The method of claim 11further comprising the step of: extruding said melt material over saidfirst spillover surface wherein said first spillover surface is conical.13. The method of claim 11 further comprising the step of: extrudingsaid melt material through said first distribution channel wherein saidfirst distribution channel comprises a plurality of spiral distributionchannels.
 14. The method of claim 11 further comprising the step of:providing a second spillover surface disposed adjacent to said secondplanar seal surface; providing a second distribution channel disposed insaid second spillover surface; and extruding said melt material throughsaid second distribution channel and along said second spilloversurface.
 15. The method of claim 11 wherein said second distributionchannel further comprises a plurality of spiral distribution channelssymmetrically disposed in said first spillover surface.
 16. A method offorming a film structure having at least three layers comprising thesteps of: providing a modular extrusion die assembly having at leastthree extrusion die modules, wherein a second extrusion die module isdisposed between a first extrusion die module and a third extrusion diemodule, wherein said second extrusion die module and said thirdextrusion die module comprises: a first mating portion comprising: afirst planar seal surface having an outer perimeter disposed in a plane;a first spillover surface, disposed entirely outside of said outerperimeter of said first planar seal surface and disposed, at least inpart, outside of said plane; and a first distribution channel disposedin said first seal surface, for distributing melt material along saidfirst spillover surface; and a second mating portion comprising a secondplanar seal surface having a perimeter; and extruding a first meltmaterial through said first extrusion die module, a second melt materialthrough said second extrusion die module, and a third melt materialthrough said third extrusion die module to form an extrudate having atleast three layers of material.
 17. The method of claim 16 wherein saidsecond mating portion of said second extrusion die module is disposedadjacent to said second mating portion of said third extrusion diemodule.
 18. The method of claim 16 further comprising the steps of:extruding said second melt material over said first spillover surface ofsecond extrusion die module; extruding said third melt material oversaid first spillover surface of said third extrusion die module, whereinsaid first spillover surface of said second extrusion die module andsaid first spillover surface of said third extrusion die module areconical.
 19. The method of claim 18 wherein said second mating portionof said second extrusion die module is disposed adjacent to said secondmating portion of said third extrusion die module such that said secondmelt material is encapsulated between said first melt material and saidthird melt material adjacent to said first spillover surface of saidfirst mating portion of said second extrusion die module.
 20. The methodof claim 16 further comprising the step of: providing a fourth extrusiondie module and a fifth extrusion die module wherein said fourthextrusion die module is disposed adjacent to said first extrusion diemodule and said fifth extrusion die module is disposed adjacent to saidthird extrusion die module; extruding a fourth melt material throughsaid fourth extrusion die modules; and extruding a fifth melt materialthrough said fifth extrusion die module to form a five layer filmstructure.